encode and decode byte array as url parameter

What I am doing is capturing a biometric information ,returns a byte[] so I needed to convert it from
byte[] to a string that I could set as a url parameter and passing it as url parameter, so &m=(biometric info).

in the receiving servlet , i am able to decode to string.
my question is how how to get the actual byte array value in the servlet.

Base-64 encoding (which the Apache Commons Compress library can handle) turns a byte[] into something that can be passed around as part of an URL. Keep in mind that URL parameters may be limited in length; you shouldn't assume that you can use more than 1KB or so.